Preventing Fruit Rots and Spray-associated Lenticel Issues in Apples Srdjan Acimovic, PhD David Rosenberger, PhD Hudson Valley Research Laboratory Empire EXPO, Syracuse 17 Jan 2018 Outline • Preventing fruit rots • Black rot • White rot • Bitter rot • Management • Spray lenticel issues • Lenticel look & function • Known spray causes • Unknown • Distinguish • What can you do? Preventing fruit rots - Fungi - • Black rot (Botryosphaeria obtusa) • White rot (Botryosphaeria dothidea) • Bitter rot (Colletotrichum spp.) • Gray mold (Botrytis cinerea) –will not cover today • All these fungi can later become storage- decays Photo by D. Rosenberger Black Rot - B. obtusa - Red Delicious Cortland - Frogeye leaf spot Gala Photo by D. Rosenberger Black Rot - B. obtusa - • Overwinters in cankers, mummy fruitlets, dead bark, brush, trunk cankers (internal fungi decay), multiple hosts • Infects fruit at warm rains (Spring: perithecia, Summer: pycnidia) • Infects from petal fall - Harvest Photo by D. Rosenberger • Forms dormant infections • Fruit ripening activates the fungus • It is a firm rot, mostly drier • It inhabits fruitlet mummies after thinning Photo by D. Rosenberger • Lenticel infections occur on semi-mature fruit during summer • These infections are visible as lenticel spots • Later it can activate and continue to cause decay in storage • Lenticel spots caused by white rot, black rot, and bitter rot possible if spray residue was lost before harvest. White rot - B. dothidea - Photo by D. Rosenberger White rot - B. dothidea - • Overwintering same as black rot • Causes infections in hot summer days • Soft rot (soggy, drippy fruit) • Has irregular margins • White rot on fruit in fall is firm similar to black rot • It causes shallow bark cankers (trunk, branches) • Typical sign is flaky bark on the trunk • Drought stress helps trunk and branch infections (Schoeneweiss 1981) • Do herbicides that hit trunk drought-stress the tree? Black & White rot - Management - • Good orchard sanitation: • Prune, remove, burn, cankers & mummies • Brush should not be left flail mowed • Avoid pruning stubs • Prevent fruit bruising • Fungicides • QoI (FRAC 11) • Thiophanates (FRAC 1) • Phthalimides (FRAC M4 – multi-site contact activity) Top choice products • Topsin-M/ Thiophanate Methyl + Captan (8 - 16 oz + 2.5 lb) • Topsin alone no bitter rot control • Flint + Captan (1.5 - 2.5 oz + 2.5 lb, also SBFS, bitter rot) • Luna Sensation 4 - 5.8 oz (also SBFS, bitter rot) • Merivon 4 - 5.5 oz (also SBFS, bitter rot) • Sovran (3.2 - 6.4 oz + 2.5 lb, also SBFS, bitter rot) • Pristine 14.5 - 18.5 oz (also SBFS, bitter rot) • Do not miss 10-15 July (based on lower Hudson Valley weather conditions) • You must re-cover after >2 inch rain • Make sure the residue is maintaened on the fruit until harvest • Problem in organic orchards: liquid-lime sulfur for SBFS, oil (~1%), damage fruit skin • Therefore fruit surface injury worsens rots in organic orchards Bitter rot - Colletotrichum spp. - More Bitter Rot? - Why? - • Rare before mancozeb 77 PHI • Dorman infection? • Hot, humid summers • Heat fruit injury? • Susceptible cultivars • Sunny side infections? • Late-maturing cultivars • Different species – biology? • More sprays Sep - Oct • Different management? • Less problems in North NY • Overwintering in NY? • Relative importance of infection sources? • Worse on drought-stressed trees • Fruit injury • Irrigate ahead of heat waves? • Spread rapidly if no fungicides • Fruit cooling - overhead nets? • Small bitter rot lesions near harvest • Storage incidence West NY Bitter Rot Species on Apples in the US - We do not know which species of fungi we have in NY - Colletotrichum acutatum complex: • C. fioriniae (Clade 2) • C. nymphaeae (Clade 3) • C. acutatum (Clade 4) • C. parananse, C. melonis, C. acerbum, C. godetiae, C. pyricola, C. rhombiforme, C. salicis, C. piri C. gloeosporioides complex (Glomerella cingulata) • C. gloeosporioides • C. siamense • C. theobromicola • C. fructicola • C. alienum • C. aenigma C. boninense complex • C. karstii *Yellow ones are reported in literature to infect apple fruit Do we have C. gelosporoides? - We do not know which fungi cause bitter rot in New York - • We found Glomerella leaf spot in Warwick, NY • It is a exual stage of C. gloeosporioides • Found on Fuji, Jonagold • It caused low crown defoliation • C. acutatum is reported to predominated in cooler regions vs. C. gloeosporioides that is predominant in warmer regions Management - Why sp. matters? - • Colletotrichum species vary in fungicide sensitivity • C. gloeosporioides complex are susceptible to benzimidazoles vs. C. acutatum complex (Topsin M) • The same is for: Rally, Flint, Captan • Topsin M does not control bitter rot • Also susceptibility to DMI-s (triazoles) varies as well depending on species • Vary in resistance to QoI, SDHI-s: Fontelis good on Ca, not Cg • There are location-related differences in which bitter rot species are present • If fruit is stored below 41°F, and sold before senescence, bitter rot might not be an issue • C. acutatum complex species grow below 41°F Management - Options - • Sources of infection: Many wild hosts hedgerows, woods • Remove dead wood, brush • Remove floor decayed fruit • Maintain grass strip below trees – it helps decay rotten fruit on the ground • Thinned fruit left hanging in the canopy give inoculum for ripening fruit on the tree • Fungicides • Use full rates of Captan if used alone • Ziram • QoI-s + captan • Flint, Merivon, Luna Sensation, Sovran, Pristine • C. acutatum clade more tolerant to Topsin, Rally, trifloxystrobin, captan Management - What if - • Spray from 10-15 July until harvest (based on lower Hudson Valley weather conditions and disease pressures) • Where bitter rot shows on a valuable cultivar spray full rate of Captan + 18.5 oz /A of Pristine or 5.5 oz/A Merivon, or Luna Sensation 5.8 oz/A, add LI-700 to enhance fruit coverage • Repeat as 10-14 day intervals • Maintain fungicide coverage up until harvest (Honeycrisp) • October sprays are a must for late maturing cultivars • If more than 2 inches of rain occur you have to respray • Cut fire blight strikes out • Storage incidence happened in fall 2016 in West NY: stem and calyx infections established in Fall 2016 • Cool fruit below 40°F immediately • Postharvest use of Scholar (fludioxonil) an option only for freshly initiated infections • It will not kill the fungus once it has penetrated in the fruit Outline • Preventing fruit rots • Black rot • White rot • Bitter rot • Management • Spray lenticel issues • Lenticel look & function • Known spray causes • Unknown • Distinguish • What can you do? Spray-related Lenticel Issues - Causes - • Extremely difficult to diagnose in storage (when we get questions about it) • Slightly easier to diagnose in orchard • Lenticel damage is also caused by environmental factors • Later change of symptoms can happen due to secondary fungi, further complicating the diagnosis • Lenticel is a porous tissue of cells with large intercellular spaces in the periderm of the secondarily thickened organs • Functions as a pore, i.e. pathway for the direct exchange of gases between the inside tissues and atmosphere Lenticel - Dynamic Tissue - Source: Konarska 2012 Source: http://www.bio.miami.edu/dana/dox/stem.html 1. Captan + surfactant lenticel injury - Penetrating adjuvants - • Injury can happen due to uptake of captan into fruit flesh through lenticels if: • Captan applied before or after an oil (within a 2-week period) • Damage to sensitive varieties: Marshall McIntosh (West NY) • Captan + liquid calcium (contains adjuvants to allow Ca uptake and captan as well) • Captan + oil, Captan + surfactant: pesticide, thinner, nutrient (Ca) • All these allow captan (toxicant) to penetrate into lenticels • When heavy rain after drought occurs, and inconsistent water supply is provided, fruit rapidly expand, lenticels crack thus allowing uptake of captan • Spray mix penetrates via damaged lenticels • Especially damaging when wax cracks occur on fruit, switching from hot to rainy conditions July 2010, McIntosh - Champlain Valley - Photos by D. Rosenberger Oct 2016 Marshall McIntosh - Champlain Valley - Photos by Anna Wallis 2. Lenticel injury - Copper Sprays - Liberty - • Summer copper sprays in dilute sprays and/or at high rates can cause the injury • Common in organic orchards • Occurs in conventional orchards when low- rate copper sprays are used for shoot blight sprays • Copper spray from bloom and 4th cover (~July 4 in NY) causes blackening at the lenticels. Photo by D. Rosenberger 3. Lenticel injury - Calcium Spray - Calcium burn - Photos by Curry et al Photos by Meheriuk et al 1994 Spray Considerations – What Promotes Lenticel Injury? - Diagnosis in orchard - • Time of day when sprayed - slow drying more uptake • Shaded sides of fruit have very thin cuticle, slower drying after sprays, or are residues are redistributed by rainfall • Lower crown = higher dose, slow drying, more injury on fruit • Products applied at too high temperatures • Crown position and side of fruit closer to sprayer before harvest? • High-velocity airblast sprayers might infuse spray materials into lenticel? • Distinguish: stink bug damage mostly on stem end half of the fruit (clustered on a shoulder due to feeding under a leaf) 4. Lenticel injury - Unknown Causes - Photos by D. Rosenberger (Rome) Empire (spray during the latter half of the season) 4. Lenticel injury - Unknown Causes- 4. Lenticel injury - Unknown Causes- Photos by D. Rosenberger (Rome) Observations by Dr.